1. Field of the Invention
This invention relates in general to the field of cellular communications, and more particularly to an apparatus and method for precluding problems associated with notifying a mobile station of an incoming call over a packetized data radio link.
2. Description of the Related Art
The cell phone industry is undergoing exponential growth, not only in this country, but all over the world. In fact, it is well known that the over twenty percent of the adult population in the United States do not even have a traditional landline telephone. In addition to those who do not own a conventional telephone, nearly ninety percent of the adult population owns a wireless phone.
And the usage of cell phones is increasing as well over the use of traditional landline telephone coverage. In fact, one in seven adults now uses only cell phones. Whereas in the past cell phones were used when a landline was not available or under emergency conditions, lower carrier rates, affordability of family packages, and free mobile-to-mobile or friend-to-friend promotions have fostered in significant increases in usage. It is not uncommon today to walk into any public forum or facility and notice a majority of the people there talking on their cell phones.
The ability to communicate using a mobile phone, or mobile station, has been available since the middle of the last century. However, during the 1990's so-called “2G” or second generation mobile phone systems were provided that began the growth in both deployment and usage that we currently enjoy today. These initial systems predominately provided for the routing and reliable servicing of voice calls between parties. And, as one skilled in the art will appreciate, there are a number of timing and latency requirements associated with transmission and reception of voice data in order to maintain quality of service. As such, so-called circuit switched voice links have been fielded that guarantee this quality of service.
And although wireless cellular network technologies have continued to provide improvements related to the ability to process voice calls, there has also been an enormous pull on the industry to provide for the reliable and efficient transfer of packetized data. As a result, the incremental developments in high speed packetized data networks have not always tracked with the development of voice networks. It is a goal within the industry to field a more unified solution that would provide both reliable voice and high speed data access, however, the industry is not at that point presently. Consequently, it is common practice to field a mobile system that provides for voice communications over one type of circuit switched network, say CDMA2000 1×RTT, and high speed data communications over another type of network, say LTE, which provides exclusively for packetized data and does not provide the quality of service that users prefer to support voice communications. In the near future, these hybrid solutions will be prevalent within the art. Currently, a mobile station (i.e., a cell phone) that is capable of communicating over two distinctly different networks as alluded to above is known as a “dual mode” mobile station.
In order to field such a hybrid system, designers are forced to develop protocols for those instances where two or more co-fielded networks create conflict, or where two or more co-fielded networks are required to interoperate.
This application deals with one such instance, that is, the switching between a high speed data network that provides exclusively for packetized data communications over to a circuit switched voice network in order to process an incoming or outgoing call, or some other event that requires use of the circuit switched network.
Presently, protocols exist for fallback to a circuit switched network during a high speed data session in order to process an incoming or outgoing call. Most present day techniques follow a form of “tunneling,” where notification data associated with the call is encapsulated into a sequence of data units that are exchanged over the packetized data network. Current provisions encapsulate essential data such as addressing and authentication information when notifying a mobile station of the call over the circuit switched link. One such protocol is defined in the 3rd Generation Partnership Project 2 (3GPP2) Specification 3GPP2 C.S0097-0, Version 1.0, April, 2010, entitled “E-UTRAN-cdma2000 1× Connectivity and Interworking Air Interface Specification” © (hereinafter referred to as “Specification”), which is herein incorporated by reference for all intents and purposes. The Specification prescribes a compatibility standard for facilitating cdma2000 1× tunneling through any radio access technology (RAT), but not through High Rate Packetized Data (HRPD), and includes requirements on the Evolved Terrestrial Radio Access Network (E-UTRAN) and cdma2000 1× interworking. In addition to architectural reference models, layered tunneling model, and requirements for equipment, particularly mobile stations and interworking solutions (IWSs), a generic circuit services notification application (GCSNA) protocol is specified to support signaling transactions for cdma2000 1× circuit switched services between mobile stations and a 1× circuit switched IWS via any RAT which provides for a tunnel between the mobile stations and the IWS. The GCSNA protocol allows a dual mode mobile station that is registered with the 1× circuit switched system to enjoy the speed benefits of packetized data services over so-called 4G Long Term Evolution (LTE) networks (which employ E-UTRAN as the air interface for high speed packetized data services), while providing a fallback protocol to enable a mobile station to initiate and receive voice calls over the 1× circuit switched system.
Notwithstanding the desirable features that GCSNA provides for switching from LTE to 1×, the present inventors have observed that this protocol lacks the robust capabilities to function in poor coverage environments, particularly those in which packetized data units (PDUs) can be lost. More specifically, because the Specification allows network designers the flexibility to prescribe certain critical parameters to on an implementation by implementation basis, the present inventors have noted that it is possible for a dual mode mobile station or IWS to receive the same packet more than once without any form of duplication detection. And as one skilled in the art will appreciate, the aforementioned undesirable consequence of duplication could cause network destabilization, mobile station lockup, and inefficient use of processing and timing resources.
Accordingly, what is needed is a technique that would eliminate the possibility of duplicate packet reception in a dual mode communications system.
In addition, what is needed is an apparatus an method that provides for reliable GCSNA tunneling transactions between a mobile station and an interworking solution over a dual mode communications network.